LTC3772B View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC3772B' PDF : 20 Pages View PDF
LTC3772B
Micropower No RSENSE
Constant Frequency Step-Down
DC/DC Controller
FEATURES
■ No Current Sense Resistor Required
■ High Output Currents Easily Achieved
■ Internal Soft-Start Ramps VOUT
■ Wide VIN Range: 2.75V to 9.8V
■ Low Dropout: 100% Duty Cycle
■ Constant Frequency 550kHz Operation
■ Low Ripple Pulse Skipping Operation at Light Load
■ Output Voltage as Low as 0.8V
■ ±1.5% Voltage Reference Accuracy
■ Current Mode Operation for Excellent Line and Load
Transient Response
■ Only 8µA Supply Current in Shutdown
■ Low Profile 8-Lead SOT-23 (1mm) and
(3mm × 2mm) DFN (0.75mm) Packages
U
APPLICATIO S
■ 1- or 2-Cell Li-Ion Battery-Powered Applications
■ Wireless Devices
■ Portable Computers
■ Distributed Power Systems
DESCRIPTIO
The LTC®3772B is a constant frequency current mode
step-down DC/DC controller in a low profile 8-lead SOT-23
(ThinSOTTM) and a 3mm × 2mm DFN package. The No
RSENSETM architecture eliminates the need for a current
sense resistor, improving efficiency and saving board
space.
The LTC3772B automatically switches into pulse skipping
operation at light loads. It consumes only 200µA of quies-
cent current under a no-load condition.
The LTC3772B incorporates an undervoltage lockout fea-
ture that shuts down the device when the input voltage
falls below 2V. To maximize the runtime from a battery
source, the external P-channel MOSFET is turned on
continuously in dropout (100% duty cycle). High switch-
ing frequency of 550kHz allows the use of a small inductor
and capacitors. An internal soft-start smoothly ramps the
output voltage from zero to its regulation point.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT and No RSENSE are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by
U.S. Patents including 5731694, 6127815.
TYPICAL APPLICATIO
550kHz Micropower Step-Down DC/DC Converter
680pF
20k
82.5k
ITH/RUN VIN
LTC3772B
GND PGATE
VFB
SW
22pF 174k
3.3µH
VIN
2.75V TO 9.8V
10µF
47µF
VOUT
2.5V
2A
3772B TA01
Efficiency and Power Loss vs Load Current
(Figure 5 Circuit)
100
10
90
80
EFFICIENCY
1
70
60
50
0.1
40
POWER LOSS
30
0.01
20
10
VIN = 3.3V
VIN = 5V
0
0.001
1
10
100
1000 10000
LOAD CURRENT (mA)
3772B TA01b
3772bfa
1
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